fs: refactor stats array to be more generic

[joyeecheung]

I have a WIP for BigInt integration of fs.Stats, which depends on the v8 6.7 update. This is part of the integration that does not depend on BigInt and does not change the API, but makes the related code more generic and reference less magic numbers and global variables.

• Pass kFsStatsFieldsLength between JS and C++ instead of using the
  magic number 14
• Pass the global stats array to the completion callback of
  asynchronous FSReqWrap similar to how the stats arrays are passed
  to the FSReqPromise resolvers
• Abstract the stats converter and take an offset to compute the
  old stats in fs.watchFile
• Use templates in node::FillStatsArray and FSReqPromise in preparation
  for BigInt intergration
• Put the global stat array filler in node_internals.h because it is
  shared by node_file.cc and node_stat_watcher.cc

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

[joyeecheung]

CI: https://ci.nodejs.org/job/node-test-pull-request/13961/

[mscdex]

Did you run fs benchmarks after these changes?

[joyeecheung]

Benchmark CI id is 149 (pending)

[mscdex]

I mean even just locally, just the subset that would be affected by this.

[joyeecheung]

@mscdex I only ran with --filter stat

                                                         confidence improvement accuracy (*)    (**)   (***)
 fs/bench-stat-promise.js statType='fstat' n=200000                     -1.96 %       ±4.23%  ±5.79%  ±7.90%
 fs/bench-stat-promise.js statType='lstat' n=200000                     -0.16 %       ±5.32%  ±7.29%  ±9.95%
 fs/bench-stat-promise.js statType='stat' n=200000                      -0.64 %       ±5.46%  ±7.51% ±10.30%
 fs/bench-stat.js statType='fstat' n=200000                              0.90 %       ±9.29% ±12.85% ±17.75%
 fs/bench-stat.js statType='lstat' n=200000                              0.13 %       ±9.95% ±13.72% ±18.86%
 fs/bench-stat.js statType='stat' n=200000                              -1.81 %      ±10.08% ±13.87% ±19.05%
 fs/bench-statSync.js statSyncType='fstatSync' n=1000000                 1.58 %       ±5.80%  ±7.98% ±10.93%
 fs/bench-statSync.js statSyncType='lstatSync' n=1000000                 0.68 %       ±5.24%  ±7.19%  ±9.82%
 fs/bench-statSync.js statSyncType='statSync' n=1000000                 -1.29 %       ±4.17%  ±5.75%  ±7.90%

[joyeecheung]

Benchmark results, interestingly there are some significant improvements in APIs that used to reference the global statValues

https://ci.nodejs.org/job/benchmark-node-micro-benchmarks/149

                                                                                  confidence improvement accuracy (*)    (**)   (***)
 fs/bench-readdir.js n=10000                                                              **     14.16 %      ±10.35% ±13.80% ±18.03%
 fs/bench-readdirSync.js n=10000                                                                 -0.59 %       ±7.72% ±10.27% ±13.36%
 fs/bench-realpath.js pathType='relative' n=10000                                                 1.34 %       ±4.77%  ±6.35%  ±8.26%
 fs/bench-realpath.js pathType='resolved' n=10000                                                -2.92 %       ±3.76%  ±5.01%  ±6.54%
 fs/bench-realpathSync.js pathType='relative' n=10000                                            -1.43 %       ±5.84%  ±7.79% ±10.18%
 fs/bench-realpathSync.js pathType='resolved' n=10000                                             1.80 %       ±4.63%  ±6.17%  ±8.05%
 fs/bench-stat.js statType='fstat' n=200000                                                       1.73 %       ±3.76%  ±5.01%  ±6.52%
 fs/bench-stat.js statType='lstat' n=200000                                                      -1.82 %       ±4.51%  ±6.01%  ±7.82%
 fs/bench-stat.js statType='stat' n=200000                                                       -0.05 %       ±5.51%  ±7.34%  ±9.56%
 fs/bench-stat-promise.js statType='fstat' n=200000                                              -0.31 %       ±3.24%  ±4.32%  ±5.64%
 fs/bench-stat-promise.js statType='lstat' n=200000                                        *     -3.51 %       ±3.14%  ±4.18%  ±5.45%
 fs/bench-stat-promise.js statType='stat' n=200000                                               -0.54 %       ±3.61%  ±4.80%  ±6.25%
 fs/bench-statSync.js statSyncType='fstatSync' n=1000000                                          0.63 %       ±4.52%  ±6.02%  ±7.84%
 fs/bench-statSync.js statSyncType='lstatSync' n=1000000                                         -0.79 %       ±1.73%  ±2.30%  ±3.00%
 fs/bench-statSync.js statSyncType='statSync' n=1000000                                    *     -2.08 %       ±1.77%  ±2.38%  ±3.14%
 fs/readfile.js concurrent=10 len=1024 dur=5                                                      1.08 %       ±1.74%  ±2.31%  ±3.01%
 fs/readfile.js concurrent=10 len=16777216 dur=5                                         ***     14.33 %       ±4.29%  ±5.71%  ±7.44%
 fs/readfile.js concurrent=1 len=1024 dur=5                                                      -0.60 %       ±3.94%  ±5.24%  ±6.82%
 fs/readfile.js concurrent=1 len=16777216 dur=5                                                  -0.23 %       ±5.58%  ±7.42%  ±9.68%
 fs/readfile-partitioned.js concurrent=10 len=1024 dur=5                                         -1.75 %       ±3.47%  ±4.61%  ±6.01%
 fs/readfile-partitioned.js concurrent=10 len=16777216 dur=5                             ***     11.81 %       ±5.55%  ±7.41%  ±9.69%
 fs/readfile-partitioned.js concurrent=1 len=1024 dur=5                                          -2.01 %       ±7.62% ±10.14% ±13.20%
 fs/readfile-partitioned.js concurrent=1 len=16777216 dur=5                                       3.77 %       ±5.41%  ±7.20%  ±9.38%
 fs/readFileSync.js n=600000                                                                     -4.59 %       ±9.73% ±12.95% ±16.87%
 fs/read-stream-throughput.js size=1024 filesize=1048576000 encodingType='asc'                    0.23 %       ±3.44%  ±4.57%  ±5.95%
 fs/read-stream-throughput.js size=1024 filesize=1048576000 encodingType='buf'                    1.70 %       ±3.28%  ±4.36%  ±5.68%
 fs/read-stream-throughput.js size=1024 filesize=1048576000 encodingType='utf'                    2.63 %       ±2.85%  ±3.80%  ±4.95%
 fs/read-stream-throughput.js size=1048576 filesize=1048576000 encodingType='asc'                -1.42 %       ±3.62%  ±4.84%  ±6.34%
 fs/read-stream-throughput.js size=1048576 filesize=1048576000 encodingType='buf'                -5.75 %       ±9.03% ±12.04% ±15.73%
 fs/read-stream-throughput.js size=1048576 filesize=1048576000 encodingType='utf'                -2.85 %       ±9.04% ±12.03% ±15.67%
 fs/read-stream-throughput.js size=4096 filesize=1048576000 encodingType='asc'                    1.76 %       ±5.22%  ±6.98%  ±9.14%
 fs/read-stream-throughput.js size=4096 filesize=1048576000 encodingType='buf'                    3.31 %       ±4.29%  ±5.70%  ±7.42%
 fs/read-stream-throughput.js size=4096 filesize=1048576000 encodingType='utf'                    1.63 %       ±2.75%  ±3.67%  ±4.78%
 fs/read-stream-throughput.js size=65535 filesize=1048576000 encodingType='asc'                  -1.57 %       ±7.11%  ±9.46% ±12.31%
 fs/read-stream-throughput.js size=65535 filesize=1048576000 encodingType='buf'            *      8.25 %       ±7.19%  ±9.60% ±12.57%
 fs/read-stream-throughput.js size=65535 filesize=1048576000 encodingType='utf'                   0.89 %       ±9.33% ±12.41% ±16.16%
 fs/write-stream-throughput.js size=1024 encodingType='asc' dur=5                                 0.63 %       ±6.87%  ±9.15% ±11.94%
 fs/write-stream-throughput.js size=1024 encodingType='buf' dur=5                                 4.66 %      ±11.05% ±14.70% ±19.15%
 fs/write-stream-throughput.js size=1024 encodingType='utf' dur=5                                -5.44 %       ±5.99%  ±7.97% ±10.38%
 fs/write-stream-throughput.js size=1048576 encodingType='asc' dur=5                              1.16 %       ±2.16%  ±2.89%  ±3.81%
 fs/write-stream-throughput.js size=1048576 encodingType='buf' dur=5                             -5.16 %      ±28.00% ±37.26% ±48.50%
 fs/write-stream-throughput.js size=1048576 encodingType='utf' dur=5                              1.33 %       ±4.49%  ±6.00%  ±7.88%
 fs/write-stream-throughput.js size=2 encodingType='asc' dur=5                                    5.67 %      ±11.77% ±15.65% ±20.38%
 fs/write-stream-throughput.js size=2 encodingType='buf' dur=5                                   -1.05 %       ±3.79%  ±5.05%  ±6.57%
 fs/write-stream-throughput.js size=2 encodingType='utf' dur=5                                    2.24 %      ±11.13% ±14.81% ±19.30%
 fs/write-stream-throughput.js size=65535 encodingType='asc' dur=5                               -5.43 %       ±9.26% ±12.33% ±16.05%
 fs/write-stream-throughput.js size=65535 encodingType='buf' dur=5                                8.24 %      ±13.55% ±18.04% ±23.49%
 fs/write-stream-throughput.js size=65535 encodingType='utf' dur=5                               -9.02 %      ±10.15% ±13.50% ±17.57%

[joyeecheung]

Rebased to address the conflicts with the newly-applied spaced-comment eslint rules.

CI: https://ci.nodejs.org/job/node-test-pull-request/13977/

[joyeecheung]

Rebased. CI: https://ci.nodejs.org/job/node-test-pull-request/14028/

[joyeecheung]

CI is green, landing..

[joyeecheung]

Landed in f7049a2, thanks!